Background and Objectives: Orienting its approach based on Islamic viewpoint (Quran and Hadith), this study aimed to investigate effectiveness of forgiveness therapy, inclination to forgive, and marital adjustment in affected women who referred to counseling centers in Tehran. Methods: This study was a semi-experimental research which made use of test-retest methodology and control group. Statistical population contained women who had suffered unfaithfulness by their husbands and referred to counseling centers of Tehran in the summer 2015. A number of 30 samples were selected in purposive and convenience manners and were categorized in two test and control groups. After conduction of pretest, which applied Spanier Dyadic Adjustment Scale and Amnesty Ray et al., members of the test group attended in nine 90-minute weekly sessions of forgiveness therapy based on Islamic viewpoint. Finally, posttest was conducted on both groups with the same tool. Results: Results of multivariable analysis of covariance showed that forgiveness therapy based on Islamic viewpoint has a significant effect on increased levels of willingness to forgive and marital adjustment in women. Conclusion: The results showed that forgiveness therapy based on Islamic viewpoints could be applied in designation of therapeutic interventions.